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Fetal Position and Presentation

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Presentation on theme: "Fetal Position and Presentation"— Presentation transcript:

The mechanism of normal labour By Dr. sallama kamel

MECHANISM OF LABOUR (NORMAL & ABNORMAL)

Chapter 22: processes and stages of labor and birth

Fetal Malpresentation

Normal Labor and Delivery

MALPRESENTATION &MALPOSITION.

Abnormal labor Li Ruzhi Ob&Gy Hospital, Fudan University.

The course and conduct of normal labor and delivery

Malpresentation Dr. Abdalla H. Elsadig MD. Definitions Presentation: Presentation: Is the lowermost part of the fetus occupying the lower uterine segment.

Malpresentaton and Breech presentation. Definitions Position The relationship of a defined area on the presenting part to the mother’s pelvis (Denominator)

Special Tutorial programme Professor Deirdre Murphy Trinity College.

MECHANISM OF LABOUR Lateefa Al Dakhyel FRCSC, FACOG Assistant professor & consultant Obstetric & gynecology department Collage of medicine King Saud University.

Dr. Udin Sabarudin Department of Obstetrics & Gynecology Medicine School of Padjadjaran University Bandung MECHANISM OF LABOR IN BREECH PRESENTATION.

ABNORMAL PRESENTATION

Abdominal Palpation for Fetal Position

Dr. ROZHAN YASSIN KHALIL FICOG,CABOG, HDOG, MBChB 2011.

Malpresentaion.

BREECH PRESENTATION.

Prof. Abdulhafid Abudher MBBch,DGO,MD,FABOG,FRCOG.

Mechanism of labor abnormal presentation and breech

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• Mammary Glands
• Fallopian Tubes
• Supporting Ligaments
• Reproductive System
• Gametogenesis
• Placental Development
• Maternal Adaptations
• Menstrual Cycle
• Antenatal Care
• Small for Gestational Age
• Large for Gestational Age
• RBC Isoimmunisation
• Prematurity
• Prolonged Pregnancy
• Multiple Pregnancy
• Miscarriage
• Recurrent Miscarriage
• Ectopic Pregnancy
• Hyperemesis Gravidarum
• Gestational Trophoblastic Disease
• Breech Presentation
• Abnormal lie, Malpresentation and Malposition
• Oligohydramnios
• Polyhydramnios
• Placenta Praevia
• Placental Abruption
• Pre-Eclampsia
• Gestational Diabetes
• Headaches in Pregnancy
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• Thyroid Disease in Pregnancy
• Epilepsy in Pregnancy
• Induction of Labour
• Operative Vaginal Delivery
• Prelabour Rupture of Membranes
• Caesarean Section
• Shoulder Dystocia
• Cord Prolapse
• Uterine Rupture
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• Secondary PPH
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• Fitting an IUS or IUD

Abnormal Fetal lie, Malpresentation and Malposition

Original Author(s): Anna Mcclune Last updated: 1st December 2018 Revisions: 12

• 1 Definitions
• 2 Risk Factors
• 3.2 Presentation
• 3.3 Position
• 4 Investigations
• 5.1 Abnormal Fetal Lie
• 5.2 Malpresentation
• 5.3 Malposition

The lie, presentation and position of a fetus are important during labour and delivery.

In this article, we will look at the risk factors, examination and management of abnormal fetal lie, malpresentation and malposition.

Definitions

• Longitudinal, transverse or oblique
• Cephalic vertex presentation is the most common and is considered the safest
• Other presentations include breech, shoulder, face and brow
• Usually the fetal head engages in the occipito-anterior position (the fetal occiput facing anteriorly) – this is ideal for birth
• Other positions include occipito-posterior and occipito-transverse.

Note: Breech presentation is the most common malpresentation, and is covered in detail here .

Fig 1 – The two most common fetal presentations: cephalic and breech.

Risk Factors

The risk factors for abnormal fetal lie, malpresentation and malposition include:

• Multiple pregnancy
• Uterine abnormalities (e.g fibroids, partial septate uterus)
• Fetal abnormalities
• Placenta praevia
• Primiparity

Identifying Fetal Lie, Presentation and Position

The fetal lie and presentation can usually be identified via abdominal examination. The fetal position is ascertained by vaginal examination.

For more information on the obstetric examination, see here .

• Face the patient’s head
• Place your hands on either side of the uterus and gently apply pressure; one side will feel fuller and firmer – this is the back, and fetal limbs may feel ‘knobbly’ on the opposite side

Presentation

• Palpate the lower uterus (above the symphysis pubis) with the fingers of both hands; the head feels hard and round (cephalic) and the bottom feels soft and triangular (breech)
• You may be able to gently push the fetal head from side to side

The fetal lie and presentation may not be possible to identify if the mother has a high BMI, if she has not emptied her bladder, if the fetus is small or if there is polyhydramnios .

During labour, vaginal examination is used to assess the position of the fetal head (in a cephalic vertex presentation). The landmarks of the fetal head, including the anterior and posterior fontanelles, indicate the position.

Fig 2 – Assessing fetal lie and presentation.

Investigations

Any suspected abnormal fetal lie or malpresentation should be confirmed by an ultrasound scan . This could also demonstrate predisposing uterine or fetal abnormalities.

Abnormal Fetal Lie

If the fetal lie is abnormal, an external cephalic version (ECV) can be attempted – ideally between 36 and 38 weeks gestation.

ECV is the manipulation of the fetus to a cephalic presentation through the maternal abdomen.

It has an approximate success rate of 50% in primiparous women and 60% in multiparous women. Only 8% of breech presentations will spontaneously revert to cephalic in primiparous women over 36 weeks gestation.

Complications of ECV are rare but include fetal distress , premature rupture of membranes, antepartum haemorrhage (APH) and placental abruption. The risk of an emergency caesarean section (C-section) within 24 hours is around 1 in 200.

ECV is contraindicated in women with a recent APH, ruptured membranes, uterine abnormalities or a previous C-section .

Fig 3 – External cephalic version.

Malpresentation

The management of malpresentation is dependent on the presentation.

• Breech – attempt ECV before labour, vaginal breech delivery or C-section
• Brow – a C-section is necessary
• If the chin is anterior (mento-anterior) a normal labour is possible; however, it is likely to be prolonged and there is an increased risk of a C-section being required
• If the chin is posterior (mento-posterior) then a C-section is necessary
• Shoulder – a C-section is necessary

Malposition

90% of malpositions spontaneously rotate to occipito-anterior as labour progresses. If the fetal head does not rotate, rotation and operative vaginal delivery can be attempted. Alternatively a C-section can be performed.

• Usually the fetal head engages in the occipito-anterior position (the fetal occiput facing anteriorly) - this is ideal for birth

If the fetal lie is abnormal, an external cephalic version (ECV) can be attempted - ideally between 36 and 38 weeks gestation.

• Breech - attempt ECV before labour, vaginal breech delivery or C-section

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Chapter 15:  Abnormal Cephalic Presentations

Jessica Dy; Darine El-Chaar

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Malpresentations.

• TRANSVERSE POSITIONS OF THE OCCIPUT
• POSTERIOR POSITIONS OF THE OCCIPUT
• BROW PRESENTATIONS
• MEDIAN VERTEX PRESENTATIONS: MILITARY ATTITUDE
• FACE PRESENTATION
• SELECTED READING
• Full Chapter
• Supplementary Content

The fetus enters the pelvis in a cephalic presentation approximately 95 percent to 96 percent of the time. In these cephalic presentations, the occiput may be in the persistent transverse or posterior positions. In about 3 percent to 4 percent of pregnancies, there is a breech-presenting fetus (see Chapter 25 ). In the remaining 1 percent, the fetus may be either in a transverse or oblique lie (see Chapter 26 ), or the head may be extended with the face or brow presenting.

Predisposing Factors

Maternal and uterine factors.

Contracted pelvis: This is the most common and important factor

Pendulous maternal abdomen: If the uterus and fetus are allowed to fall forward, there may be difficulty in engagement

Neoplasms: Uterine fibromyomas or ovarian cysts can block the entry to the pelvis

Uterine anomalies: In a bicornuate uterus, the nonpregnant horn may obstruct labor in the pregnant one

Abnormalities of placental size or location: Conditions such as placenta previa are associated with unfavorable positions of the fetus

High parity

Fetal Factors

Errors in fetal polarity, such as breech presentation and transverse lie

Abnormal internal rotation: The occiput rotates posteriorly or fails to rotate at all

Fetal attitude: Extension in place of normal flexion

Multiple pregnancy

Fetal anomalies, including hydrocephaly and anencephaly

Polyhydramnios: An excessive amount of amniotic fluid allows the baby freedom of activity, and he or she may assume abnormal positions

Prematurity

Placenta and Membranes

Placenta previa

Cornual implantation

Premature rupture of membranes

Effects of Malpresentations

Effects on labor.

The less symmetrical adaptation of the presenting part to the cervix and to the pelvis plays a part in reducing the efficiency of labor.

The incidence of fetopelvic disproportion is higher

Inefficient uterine action is common. The contractions tend to be weak and irregular

Prolonged labor is seen frequently

Pathologic retraction rings can develop, and rupture of the lower uterine segment may be the end result

The cervix often dilates slowly and incompletely

The presenting part stays high

Premature rupture of the membranes occurs often

The need for operative delivery is increased

Effects on the Mother

Because greater uterine and intraabdominal muscular effort is required and because labor is often prolonged, maternal exhaustion is common

There is more stretching of the perineum and soft parts, and there are more lacerations

Tears of the uterus, cervix, and vagina

Uterine atony from prolonged labor

Early rupture of the membranes

Excessive blood loss

Tissue damage

Frequent rectal and vaginal examinations

Prolonged labor

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Position and Presentation of the Fetus

• IN THIS TOPIC

Labour and Delivery Care Module: 8. Abnormal Presentations and Multiple Pregnancies

Study session 8  abnormal presentations and multiple pregnancies, introduction.

In previous study sessions of this module, you have been introduced to the definitions, signs, symptoms and stages of normal labour, and about the ‘normal’ vertex presentation of the fetus during delivery. In this study session, you will learn about the most common abnormal presentations (breech, shoulder, face or brow), their diagnostic criteria and the required actions you need to take to prevent complications developing during labour. Taking prompt action may save the life of the mother and her baby if the delivery becomes obstructed because the baby is in an abnormal presentation. We will also tell you about twin births and the complications that may result if the two babies become ‘locked’ together, preventing either of them from being born.

Learning Outcomes for Study Session 8

After studying this session, you should be able to:

8.1  Define and use correctly all of the key words printed in bold . (SAQs 8.1 and 8.2)

8.2  Describe how you would identify a fetus in the vertex presentation and distinguish this from common malpresentations and malpositions. (SAQs 8.1 and 8.2)

8.3  Describe the causes and complications for the fetus and the mother of fetal malpresentation during full term labour. (SAQ 8.3)

8.4  Describe how you would identify a multiple pregnancy and the complications that may arise. (SAQ 8.4)

8.5  Explain when and how you would refer a woman in labour due to abnormal fetal presentation or multiple pregnancy. (SAQ 8.4)

8.1  Normal and abnormal presentations

8.1.1  vertex presentation.

In about 95% of deliveries, the part of the fetus which arrives first at the mother’s pelvic brim is the highest part of the fetal head, which is called the vertex (Figure 8.1). This presentation is called the vertex presentation . Notice that the baby’s chin is tucked down towards its chest, so that the vertex is the leading part entering the mother’s pelvis. The baby’s head is said to be ‘well-flexed’ in this position.

During early pregnancy, the baby is the other way up — with its bottom pointing down towards the mother’s cervix — which is called the breech presentation . This is because during its early development, the head of the fetus is bigger than its buttocks; so in the majority of cases, the head occupies the widest cavity, i.e. the fundus (rounded top) of the uterus. As the fetus grows larger, the buttocks become bigger than the head and the baby spontaneously reverses its position, so its buttocks occupy the fundus. In short, in early pregnancy, the majority of fetuses are in the breech presentation and later in pregnancy most of them make a spontaneous transition to the vertex presentation.

8.1.2  Malpresentations

You will learn about obstructed labour in Study Session 9.

When the baby presents itself in the mother’s pelvis in any position other than the vertex presentation, this is termed an abnormal presentation, or m alpresentation . The reason for referring to this as ‘abnormal’ is because it is associated with a much higher risk of obstruction and other birth complications than the vertex presentation. The most common types of malpresentation are termed breech, shoulder, face or brow. We will discuss each of these in turn later. Notice that the baby can be ‘head-down’ but in an abnormal presentation, as in face or brow presentations, when the baby’s face or forehead (brow) is the presenting part.

8.1.3  Malposition

Although it may not be so easy for you to identify this, the baby can also be in an abnormal position even when it is in the vertex presentation. In a normal delivery, when the baby’s head has engaged in the mother’s pelvis, the back of the baby’s skull (the occiput ) points towards the front of the mother’s pelvis (the pubic symphysis ), where the two pubic bones are fused together. This orientation of the fetal skull is called the occipito-anterior position (Figure 8.2a). If the occiput (back) of the fetal skull is towards the mother’s back, this occipito-posterior position (Figure 8.2b) is a vertex malposition , because it is more difficult for the baby to be born in this orientation. The good thing is that more than 90% of babies in vertex malpositions undergo rotation to the occipito-anterior position and are delivered normally.

You learned the directional positions: anterior/in front of and posterior/behind or in the back of, in the Antenatal Care Module, Part 1, Study Session 3.

Note that the fetal skull can also be tilted to the left or to the right in either the occipito-anterior or occipito-posterior positions.

8.2  Causes and consequences of malpresentations and malpositions

In the majority of individual cases it may not be possible to identify what caused the baby to be in an abnormal presentation or position during delivery. However, the general conditions that are thought to increase the risk of malpresentation or malposition are listed below:

Multiple pregnancy is the subject of Section 8.7 of this study session. You learned about placenta previa in the Antenatal Care Module, Study Session 21.

• Abnormally increased or decreased amount of amniotic fluid
• A tumour (abnormal tissue growth) in the uterus preventing the spontaneous inversion of the fetus from breech to vertex presentation during late pregnancy
• Abnormal shape of the pelvis
• Laxity (slackness) of muscular layer in the walls of the uterus
• Multiple pregnancy (more than one baby in the uterus)
• Placenta previa (placenta partly or completely covering the cervical opening).

If the baby presents at the dilating cervix in an abnormal presentation or malposition, it will more difficult (and may be impossible) for it to complete the seven cardinal movements that you learned about in Study Sessions 3 and 5. As a result, birth is more difficult and there is an increased risk of complications, including:

You learned about PROM in Study Session 17 of the Antenatal Care Module, Part 2.

• Premature rupture of the fetal membranes (PROM)
• Premature labour
• Slow, erratic, short-lived contractions
• Uncoordinated and extremely painful contractions, with slow or no progress of labour
• Prolonged and obstructed labour, leading to a ruptured uterus (see Study Sessions 9 and 10 of this Module)
• Postpartum haemorrhage (see Study Session 11)
• Fetal and maternal distress, which may lead to the death of the baby and/or the mother.

With these complications in mind, we now turn your attention to the commonest types of malpresentation and how to recognise them.

8.3  Breech presentation

In a b reech presentation , the fetus lies with its buttocks in the lower part of the uterus, and its buttocks and/or the feet are the presenting parts during delivery. Breech presentation occurs on average in 3–4% of deliveries after 34 weeks of pregnancy.

When is the breech position the normal position for the fetus?

During early pregnancy the baby’s bottom points down towards the mother’s cervix, and its head (the largest part of the fetus at this stage of development) occupies the fundus (rounded top) of the uterus, which is the widest part of the uterine cavity.

8.3.1  Causes of breech presentation

You can see a transverse lie in Figure 8.7 later in this study session.

In the majority of cases there is no obvious reason why the fetus should present by the breech at full term. In practice, what is commonly observed is the association of breech presentation at delivery with a transverse lie earlier in the pregnancy, i.e. the fetus lies sideways across the mother’s abdomen, facing a sideways implanted placenta. It is thought that when the placenta is in front of the baby’s face, it may obstruct the normal process of inversion, when the baby turns head-down as it gets bigger during the pregnancy. As a result, the fetus turns in the other direction and ends in the breech presentation. Some other circumstances that are thought to favour a breech presentation during labour include:

• Premature labour, beginning before the baby undergoes spontanous inversion from breech to vertex presentation
• Multiple pregnancy, preventing the normal inversion of one or both babies
• Polyhydramnios: excessive amount of amniotic fluid, which makes it more difficult for the fetal head to ‘engage’ with the mother’s cervix (polyhydramnios is pronounced ‘poll-ee-hy-dram-nee-oss’. Hydrocephaly is pronounced ‘hy-droh-keff-all-ee’)
• Hydrocephaly (‘water on the brain’) i.e. an abnormally large fetal head due to excessive accumulation of fluid around the brain
• Placenta praevia
• Breech delivery in the previous pregnancy
• Abnormal formation of the uterus.

8.3.2  Diagnosis of breech presentation

On abdominal palpation the fetal head is found above the mother’s umbilicus as a hard, smooth, rounded mass, which gently ‘ballots’ (can be rocked) between your hands.

Why do you think a mass that ‘ballots’ high up in the abdomen is a sign of breech presentation? (You learned about this in Study Session 11 of the Antenatal Care Module.)

The baby’s head can ‘rock’ a little bit because of the flexibility of the baby’s neck, so if there is a rounded, ballotable mass above the mother’s umbilicus it is very likely to be the baby’s head. If the baby was ‘bottom-up’ (vertex presentation) the whole of its back will move of you try to rock the fetal parts at the fundus (Figure 8.3).

Once the fetus has engaged and labour has begun, the breech baby’s buttocks can be felt as soft and irregular on vaginal examination. They feel very different to the relatively hard rounded mass of the fetal skull in a vertex presentation. When the fetal membranes rupture, the buttocks and/or feet can be felt more clearly. The baby’s anus may be felt and fresh thick, dark meconium may be seen on your examining finger. If the baby’s legs are extended, you may be able to feel the external genitalia and even tell the sex of the baby before it is born.

8.3.3  Types of breech presentation

There are three types of breech presentation, as illustrated in Figure 8.4. They are:

• Complete breech is characterised by flexion of the legs at both hips and knee joints, so the legs are bent underneath the baby.
• Frank breech is the commonest type of breech presentation, and is characterised by flexion at the hip joints and extension at the knee joints, so both the baby’s legs point straight upwards.
• Footling breech is when one or both legs are extended at the hip and knee joint and the baby presents ‘foot first’.

8.3.4  Risks of breech presentation

Regardless of the type of breech presentation, there are significant associated risks to the baby. They include:

• The fetal head gets stuck (arrested) before delivery
• Labour becomes obstructed when the fetus is disproportionately large for the size of the maternal pelvis
• Cord prolapse may occur, i.e. the umbilical cord is pushed out ahead of the baby and may get compressed against the wall of the cervix or vagina
• Premature separation of the placenta (placental abruption)
• Birth injury to the baby, e.g. fracture of the arms or legs, nerve damage, trauma to the internal organs, spinal cord damage, etc.

A breech birth may also result in trauma to the mother’s birth canal or external genitalia through being overstretched by the poorly fitting fetal parts.

Cord prolapse in a normal (vertex) presentation was illustrated in Study Session 17 of the Antenatal Care Module, and placental abruption was covered in Study Session 21.

What will be the effect on the baby if it gets stuck, the labour is obstructed, the cord prolapses, or placental abruption occurs?

The result will be hypoxia , i.e. it will be deprived of oxygen, and may suffer permanent brain damage or die.

You learned about the causes and consequences of hypoxia in the Antenatal Care Module.

8.4  Face presentation

Face presentation occurs when the baby’s neck is so completely extended (bent backwards) that the occiput at the back of the fetal skull touches the baby’s own spine (see Figure 8.5). In this position, the baby’s face will present to you during delivery.

Refer the mother if a baby in the chin posterior face presentation does not rotate and the labour is prolonged.

The incidence of face presentation is about 1 in 500 pregnancies in full term labours. In Figure 8.5, you can see how flexed the head is at the neck. Babies who present in the ‘chin posterior’ position (on the right in Figure 8.5) usually rotate spontaneously during labour, and assume the ‘chin anterior’ position, which makes it easier for them to be born. However, they are unlikely to be delivered vaginally if they fail to undergo spontaneous rotation to the chin anterior position, because the baby’s chin usually gets stuck against the mother’s sacrum (the bony prominence at the back of her pelvis). A baby in this position will have to be delivered by caesarean surgery.

8.4.1  Causes of face presentation

The causes of face presentation are similar to those already described for breech births:

• Laxity (slackness) of the uterus after many previous full-term pregnancies
• Multiple pregnancy
• Polyhydramnios (excessive amniotic fluid)
• Congenital abnormality of the fetus (e.g. anencephaly, which means no or incomplete skull bones)
• Abnormal shape of the mother’s pelvis.

8.4.2  Diagnosis of face presentation

Face presentation may not be easily detected by abdominal palpation, especially if the chin is in the posterior position. On abdominal examination, you may feel irregular shapes, formed because the fetal spine is curved in an ‘S’ shape. However, on vaginal examination, you can detect face presentation because:

• The presenting part will be high, soft and irregular.
• When the cervix is sufficiently dilated, you may be able to feel parts of the face, such as the orbital ridges above the eyes, the nose or mouth, gums, or bony chin.
• If the membranes are ruptured, the baby may suck your examining finger!

But as labour progresses, the baby’s face becomes o edematous (swollen with fluid), making it more difficult to distinguish from the soft shape you will feel in a breech presentation.

8.4.3  Complications of face presentation

Complications for the fetus include:

• Obstructed labour and ruptured uterus
• Cord prolapse
• Facial bruising
• Cerebral haemorrhage (bleeding inside the fetal skull).

8.5  Brow presentation

In brow presentation , the baby’s head is only partially extended at the neck (compare this with face presentation), so its brow (forehead) is the presenting part (Figure 8.6). This presentation is rare, with an incidence of 1 in 1000 deliveries at full term.

8.5.1  Possible causes of brow presentation

You have seen all of these factors before, as causes of other malpresentations:

• Lax uterus due to repeated full term pregnancy
• Polyhydramnios

8.5.2  Diagnosis of brow presentation

Brow presentation is not usually detected before the onset of labour, except by very experienced birth attendants. On abdominal examination, the head is high in the mother’s abdomen, appears unduly large and does not descend into the pelvis, despite good uterine contractions. On vaginal examination, the presenting part is high and may be difficult to reach. You may be able to feel the root of the nose, eyes, but not the mouth, tip of the nose or chin. You may also feel the anterior fontanel, but a large caput (swelling) towards the front of the fetal skull may mask this landmark if the woman has been in labour for some hours.

Recall the appearance of a normal caput over the posterior fontanel shown in Figure 4.4 earlier in this Module.

8.5.3  Complications of brow presentation

The complications of brow presentation are much the same as for other malpresentations:

• Cerebral haemorrhage.

Which are you more likely to encounter — face or brow presentations?

Face presentation, which occurs in 1 in 500 full term labours. Brow presentation is more rare, at 1 in 1,000 full term labours.

8.6  Shoulder presentation

Shoulder presentation is rare at full term, but may occur when the fetus lies transversely across the uterus (Figure 8.7), if it stopped part-way through spontaneous inversion from breech to vertex, or it may lie transversely from early pregnancy. If the baby lies facing upwards, its back may be the presenting part; if facing downwards its hand may emerge through the cervix. A baby in the transverse position cannot be born through the vagina and the labour will be obstructed. Refer babies in shoulder presentation urgently.

8.6.1  Causes of shoulder presentation

Causes of shoulder presentation could be maternal or fetal factors.

Maternal factors include:

• Lax abdominal and uterine muscles: most often after several previous pregnancies
• Uterine abnormality
• Contracted (abnormally narrow) pelvis.

Fetal factors include:

• Preterm labour
• Placenta previa.

What do ‘placenta previa’ and ‘polyhydramnios’ indicate?

Placenta previa is when the placenta is partly or completely covering the cervical opening. Polyhydramnios is an excess of amniotic fluid. They are both potential causes of malpresentation.

8.6.2  Diagnosis of shoulder presentation

On abdominal palpation, the uterus appears broader and the height of the fundus is less than expected for the period of gestation, because the fundus is not occupied by either the baby’s head or buttocks. You can usually feel the head on one side of the mother’s abdomen. On vaginal examination, in early labour, the presenting part may not be felt, but when the labour is well progressed, you may feel the baby’s ribs. When the shoulder enters the pelvic brim, the baby’s arm may prolapse and become visible outside the vagina.

8.6.3  Complications of shoulder presentation

Complications include:

• Trauma to a prolapsed arm
• Fetal hypoxia and death.

Remember that a shoulder presentation means the baby cannot be born through the vagina; if you detect it in a woman who is already in labour, refer her urgently to a higher health facility.

8.7  Multiple pregnancy

In this section, we turn to the subject of multiple pregnancy , when there is more than one fetus in the uterus. More than 95% of multiple pregnancies are twins (two fetuses), but there can also be triplets (three fetuses), quadruplets (four fetuses), quintuplets (five fetuses), and other higher order multiples with a declining chance of occurrence. The spontaneous occurrence of twins varies by country : it is lowest in East Asia n countries like Japan and China (1 out of 1000 pregnancies are fraternal or non-identical twins), and highest in black Africans , particularly in Nigeria , where 1 in 20 pr egnancies are fraternal twins. In general, compared to single babies, multiple pregnancies are highly associated with early pregnancy loss and high perinatal mortality, mainly due to prematurity.

8.7.1  Types of twin pregnancy

Twins may be identical (monozygotic) or non-identical and fraternal (dizigotic). Monozygotic twins develop from a single fertilised ovum (the zygote), so they are always the same sex and they share the same placenta . By contrast, dizygotic twins develop from two different zygotes, so they can have the same or different sex, and they have separate placenta s . Figure 8.8 shows the types of twin pregnancy and the processes by which they are formed.

8.7.2  Diagnosis of twin pregnancy

On abdominal examination you may notice that:

• The size of the uterus is larger than the expected for the period for gestation.
• The uterus looks round and broad, and fetal movement may be seen over a large area. (The shape of the uterus at term in a singleton pregnancy in the vertex presentation appears heart-shaped rounder at the top and narrower at the bottom.)
• Two heads can be felt.
• Two fetal heart beats may be heard if two people listen at the same time, and they can detect at least 10 beats different (Figure 8.6).
• Ultrasound examination can make an absolute diagnosis of twin pregnancy.

8.7.3  Consequences of twin pregnancy

Women who are pregnant with twins are more prone to suffer with the minor disorders of pregnancy, like morning sickness, nausea and heartburn. Twin pregnancy is one cause of hyperemesis gravidarum (persistent, severe nausea and vomiting). Mothers of twins are also more at risk of developing iron and folate-deficiency anaemia during pregnancy.

Can you suggest why anaemia is a greater risk in multiple pregnancies?

The mother has to supply the nutrients to feed two (or more) babies; if she is not getting enough iron and folate in her diet, or through supplements, she will become anaemic.

Other complications include the following:

• Pregnancy-related hypertensive disorders like pre-eclampsia and eclampsia are more common in twin pregnancies.
• Pressure symptoms may occur in late pregnancy due to the increased weight and size of the uterus.
• Labour often occurs spontaneously before term, with p remature delivery or premature rupture of membranes (PROM) .
• Respiratory deficit ( shortness of breath, because of fast growing uterus) is another common problem.

Twin babies may be small in comparison to their gestational age and more prone to the complications associated with low birth weight (increased vulnerability to infection, losing heat, difficulty breastfeeding).

You will learn about low birth weight babies in detail in the Postnatal Care Module.

• Malpresentation is more common in twin pregnancies, and they may also be ‘locked’ at the neck with one twin in the vertex presentation and the other in breech. The risks associated with malpresentations already described also apply: prolapsed cord, poor uterine contraction, prolonged or obstructed labour, postpartum haemorrhage, and fetal hypoxia and death.
• Conjoined twins (fused twins, joined at the head, chest, or abdomen, or through the back) may also rarely occur.

8.8  Management of women with malpresentation or multiple pregnancy

As you have seen in this study session, any presentation other than vertex has its own dangers for the mother and baby. For this reason, all women who develop abnormal presentation or multiple pregnancy should ideally have skilled care by senior health professionals in a health facility where there is a comprehensive emergency obstetric service. Early detection and referral of a woman in any of these situations can save her life and that of her baby.

What can you do to reduce the risks arising from malpresentation or multiple pregnancy in women in your care?

During focused antenatal care of the pregnant women in your community, at every visit after 36 weeks of gestation you should check for the presence of abnormal fetal presentation. If you detect abnormal presentation or multiple pregnancy, you should refer the woman before the onset of labour.

Summary of Study Session 8

In Study Session 8, you learned that:

• During early pregnancy, babies are naturally in the breech position, but in 95% of cases they spontaneously reverse into the vertex presentation before labour begins.
• Malpresentation or malposition of the fetus at full term increases the risk of obstructed labour and other birth complications.
• Common causes of malpresentations/malpositions include: excess amniotic fluid, abnormal shape and size of the pelvis; uterine tumour; placenta praevia; slackness of uterine muscles (after many previous pregnancies); or multiple pregnancy.
• Common complications include: premature rupture of membranes, premature labour, prolonged/obstructed labour; ruptured uterus; postpartum haemorrhage; fetal and maternal distress which may lead to death.
• Vertex malposition is when the fetal head is in the occipito-posterior position — i.e. the back of the fetal skull is towards the mother’s back instead of pointing towards the front of the mother’s pelvis. 90% of vertex malpositions rotate and deliver normally.
• Breech presentation (complete, frank or footling) is when the baby’s buttocks present during labour. It occurs in 3–4% of labours after 34 weeks of pregnancy and may lead to obstructed labour, cord prolapse, hypoxia, premature separation of the placenta, birth injury to the baby or to the birth canal.
• Face presentation is when the fetal head is bent so far backwards that the face presents during labour. It occurs in about 1 in 500 full term labours. ‘Chin posterior’ face presentations usually rotate spontaneously to the ‘chin anterior’ position and deliver normally. If rotation does not occur, a caesarean delivery is likely to be necessary.
• Brow presentation is when the baby’s forehead is the presenting part. It occurs in about 1 in 1000 full term labours and is difficult to detect before the onset of labour. Caesarean delivery is likely to be necessary.
• Shoulder presentation occurs when the fetal lie during labour is transverse. Once labour is well progressed, vaginal examination may feel the baby’s ribs, and an arm may sometimes prolapse. Caesarean delivery is always required unless a doctor or midwife can turn the baby head-down.
• Multiple pregnancies are always at high risk of malpresentation. Mothers need greater antenatal care, and twins are more prone to complications associated with low birth weight and prematurity.
• Any presentation other than vertex after 34 weeks of gestation is considered as high risk to the mother and to her baby. Do not attempt to turn a malpresenting or malpositioned baby! Refer the mother for emergency obstetric care.

Self-Assessment Questions (SAQs) for Study Session 8

Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering the following questions. Write your answers in your Study Diary and discuss them with your Tutor at the next Study Support Meeting. You can check your answers with the Notes on the Self-Assessment Questions at the end of this Module.

SAQ 8.1 (tests Learning Outcomes 8.1, 8.2 and 8.4)

Which of the following definitions are true and which are false? Write down the correct definition for any which you think are false.

A  Fundus — the ‘rounded top’ and widest cavity of the uterus.

B  Complete breech — where the legs are bent at both hips and knee joints and are folded underneath the baby.

C  Frank breech — where the breech is so difficult to treat that you have to be very frank and open with the mother about the difficulties she will face in the birth.

D  Footling breech — when one or both legs are extended so that the baby presents ‘foot first’.

E  Hypoxia — the baby gets too much oxygen.

F  Multiple pregnancy — when a mother has had many babies previously.

G  Monozygotic twins — develop from a single fertilised ovum (the zygote). They can be different sexes but they share the same placenta.

H  Dizygotic twins — develop from two zygotes. They have separate placentas, and can be of the same sex or different sexes.

A is true.  The fundus is the ‘rounded top’ and widest cavity of the uterus.

B is true.  Complete breech is where the legs are bent at both hips and knee joints and are folded underneath the baby.

C is false . A frank breech is the most common type of breech presentation and is when the baby’s legs point straight upwards (see Figure 8.4).

D is true.   A footling breech is when one or both legs are extended so that the baby presents ‘foot first’.

E is false .  Hypoxia is when the baby is deprived of oxygen and risks permanent brain damage or death.

F is false.   Multiple pregnancy is when there is more than one fetus in the uterus.

G is false.   Monozygotic twins develop from a single fertilised ovum (the zygote), and they are always the same sex , as well as sharing the same placenta.

H is true.  Dizygotic twins develop from two zygotes, have separate placentas, and can be of the same or different sexes.

SAQ 8.2 (tests Learning Outcomes 8.1 and 8.2)

What are the main differences between normal and abnormal fetal presentations? Use the correct medical terms in bold in your explanation.

In a normal presentation, the vertex (the highest part of the fetal head) arrives first at the mother’s pelvic brim, with the occiput (the back of the baby’s skull) pointing towards the front of the mother’s pelvis (the pubic symphysis ).

Abnormal presentations are when there is either a vertex malposition (the occiput of the fetal skull points towards the mother’s back instead towards of the pubic symphysis), or a malpresentation (when anything other than the vertex is presenting): e.g. breech presentation (buttocks first); face presentation (face first); brow presentation (forehead first); and shoulder presentation (transverse fetal).

SAQ 8.3 (tests Learning Outcomes 8.3 and 8.5)

• a. List the common complications of malpresentations or malposition of the fetus at full term.
• b. What action should you take if you identify that the fetus is presenting abnormally and labour has not yet begun?
• c. What should you not attempt to do?
• a. The common complications of malpresentation or malposition of the fetus at full term include: premature rupture of membranes, premature labour, prolonged/obstructed labour; ruptured uterus; postpartum haemorrhage; fetal and maternal distress which may lead to death.
• b. You should refer the mother to a higher health facility – she may need emergency obstetric care.
• c. You should not attempt to turn the baby by hand. This should only be attempted by a specially trained doctor or midwife and should only be done at a health facility.

SAQ 8.4 (tests Learning Outcomes 8.4 and 8.5)

A pregnant woman moves into your village who is already at 37 weeks gestation. You haven’t seen her before. She tells you that she gave birth to twins three years ago and wants to know if she is having twins again this time.

• a. How would you check this?
• b. If you diagnose twins, what would you do to reduce the risks during labour and delivery?
• Is the uterus larger than expected for the period of gestation?
• What is its shape – is it round (indicative of twins) or heart-shaped (as in a singleton pregnancy)?
• Can you feel more than one head?
• Can you hear two fetal heartbeats (two people listening at the same time) with at least 10 beats difference?
• If there is access to a higher health facility, and you are still not sure, try and get the woman to it for an ultrasound scan.
• Be extra careful to check that the mother is not anaemic.
• Encourage her to rest and put her feet up to reduce the risk of increased blood pressure or swelling in her legs and feet.
• Be alert to the increased risk of pre-eclampsia.
• Expect her to go into labour before term, and be ready to get her to the health facility before she goes into labour, going with her if at all possible.
• Get in early touch with that health facility to warn them to expect a referral from you.
• Make sure that transport is ready to take her to a health facility when needed.

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• Introduction
• Definitions
• Perinatal Morbidity And Mortality
• Complications And Counseling
• Intrapartum Complications And Counseling
• Intrapartum Management
• Management Of Labor And Delivery
• Cesarean Delivery
• Perinatal Outcome

Abnormal Fetal Lie and Presentation

Introduction.

The normal process of parturition relies in part, on the physical relationships between the fetus and maternal bony outlet. In addition, fetal posture, placental and cord locations, as well as maternal soft tissues also are factors in the efficiency and safety of the birth process.

This chapter discusses how to define, diagnose, and manage the clinical impact of abnormalities of fetal lie and malpresentation. The most common clinical correlation of the abnormal fetal lies and presentations is the breech-presenting fetus.

DEFINITIONS

In describing fetopelvic relationships, the clinician should carefully adhere to standard obstetrical nomenclature. Fetal lie refers to the relationship between the long axis of the fetus with respect to the long axis of the mother. The possibilities include a longitudinal lie, a transverse lie, and, on occasion, an oblique lie. Fetal presentation is a reference to the part of the fetus that is overlying the maternal pelvic inlet.

The most common relationship between fetus and mother is the longitudinal lie, cephalic presentation. A breech fetus also is a longitudinal lie, with the fetal buttocks as the presenting part. Breech fetuses also are referred to as malpresentations because of the many problems associated with them. Fetuses that are in a transverse lie may present the fetal back (or shoulders, as in the acromial presentation), small parts (arms and legs), or the umbilical cord (as in a funic presentation) to the pelvic inlet. In an oblique lie, the fetal long axis is at an angle to the bony inlet, and no palpable fetal part generally is presenting. This lie usually is transitory and occurs during fetal conversion between other lies.

The most dependent portion of the presenting part is known as the point of direction. The occiput is the point of direction of a well-flexed fetus in cephalic presentation. The fetal position refers to the location of the point of direction with reference to the four quadrants of the maternal outlet as viewed by the examiner. Thus, position may be right or left as well as anterior or posterior.

Fetal attitude refers to the posture of a fetus during labor. Mammalian fetuses have a tendency to assume a fully flexed posture during development and during parturition. Flexion of the fetal head on the chest allows for the delivery of the head by its smallest bony diameter. A loss of this flexed posture presents a progressively larger fetal head to the bony pelvis for labor and delivery (Fig. 1). The fetal arms and legs also tend to assume a fully flexed posture. The longitudinal posture of the fetus likewise is flexed under normal circumstances.

The mechanism of labor and delivery, as well as its inherent safety and efficacy, is determined by the specifics of the fetopelvic relationship at the onset of labor. Further correlations with fetopelvic relationships are important before birth.

The relative incidence of differing fetopelvic relations varies with diagnostic and clinical approaches to care. Among longitudinal lies, about 1 in 25 fetuses are not cephalic but breech at the onset of labor. 1 Of the differing lies a fetus may assume, about 1 in 100 is transverse or oblique, also referred to as nonaxial.

As pregnancy proceeds to term, most fetuses assume a longitudinal lie with relationship with the maternal outlet. Conversely, when labor and delivery are considered to be remote from term, the proportion of fetuses in abnormal and suboptimal locations increases ( Table 1 ).

Table 1. Breech presentation by gestational age

Transverse and oblique lies also are seen with greater frequency earlier in gestation. A fetus in a transverse lie may present the shoulder or acromion as a point of reference to the examiner. As term approaches, spontaneous conversion to a longitudinal lie is the norm. As seen with breech presentation, there is a rapid decrease in nonaxial lie during the third trimester. With the comprehensive application of ultrasound in the antepartum period, discovery of a transverse or oblique lie has increased. However, nonaxial fetal lies usually are transitory.

Abnormal fetal lie frequently is seen in multifetal gestation, particularly with the second twin. A transverse lie may be encountered with large discrepancies in fetopelvic parameters, such as exist with extreme prematurity and macrosomia. This tendency is greater in women of grand parity, in whom relaxation of the abdominal and uterine musculature is cited as the predisposing factor. Distortion of the uterine cavity shape, such as that seen with leiomyomas, prior uterine surgery, or developmental anomalies (Mullerian fusion defects), coexists with both abnormalities in fetal lie and malpresentation. Placental location also may play a contributing role. Fundal and cornual implantation are seen more frequently in breech presentation. Placenta previa is a well-described concomitant in both transverse lie and breech presentation. 2

Congenital anomalies of the fetus also are seen in association with abnormalities in either presentation or lie. 3 Whether a cause (as in fitting the uterine cavity optimally) or effect (the fetus with a neuromuscular condition that prevents the normal turning mechanism), the finding of an abnormal lie or malpresentation requires a thorough search for fetal maldevelopment. Abnormalities seen include chromosomal (autosomal trisomy) and structural abnormalities (hydrocephalus), as well as syndromes of multiple effects (fetal alcohol syndrome) ( Table 2 ).

Table 2. Anomalies frequently diagnosed in breech fetuses

Congenital anomalies of major structures are seen in 3–5% of all births. The incidence in breech delivery is three times greater when controlled for gestational age. Among premature breech infants, the incidence is even greater, as it is for all fetuses born prematurely.

Prematurity is a crucial factor in the incidence as well as the clinical implications of abnormal fetal lie and malpresentation. Fetal size and shape undergo dramatic change during the second and third trimester (Fig. 2, Table 3 ).

Table 3. Head circumference: abdominal circumference ratio by gestational age

SD, standard deviations (Adapted from Campbell S, Metreweli C [eds]: Practical Abdominal Ultrasound. Chicago, Year Book Medical Publishers, 1978)

Because the fetus has a relatively larger head than body during most of the late second and early third trimester, the fetus tends to spend much of its time in breech presentation or in a nonaxial lie as it rotates back and forth between cephalic and breech presentations. The relatively large volume of amniotic fluid present facilitates these dynamics.

Breech presentation is more common at earlier gestation and therefore is seen more frequently among low-birth weight infants 4 ( Table 4 ). Breech infants are more likely to be small for gestational age regardless of their gestation at delivery.

Table 4. Incidence of breech presentation by birth weight

The small size of the premature fetus is further compromised by the specific malpresentations that occur. With less neurologic and muscular control, deflexed or even extended varieties of fetal presentations are seen. Most common are the “incomplete” types of breech presentation, such as footling breech presentations (Fig. 3, Tables 5 and 6 ). Deflexion of the fetal head, more commonly seen in preterm fetuses, results in the potential for further compromise at delivery.

Table 5. Varieties of breech presentation

Table 6. Type of breech presentation in labor by gestational age

(Adapted from Gimovsky M, Petrie RH: Breech presentation. In Evans M, Fletcher J, Dixler A et al [eds]: Fetal Diagnosis and Therapy, pp 276–295. Philadelphia, JB Lippincott, 1989.)

Thus, the problems associated with abnormal lie and malpresentation are most frequent and of greatest consequence in preterm labor and delivery. At term, similar, though usually less dramatic, consequences may be seen with fetuses who are in abnormal positions.

PERINATAL MORBIDITY AND MORTALITY

Perinatal morbidity and mortality is threefold higher in breech presentation than cephalic presentation. Much of this excessive compromise is caused by factors that are not directly preventable. According to Kaupilla, 5 64% of deaths among term breech infants resulted from congenital malformations or infection. In a different population, Todd and Steer 6 found that 23 of 34 term breech deaths among 1006 term infants were not related to complications of breech delivery but were associated with anomalies, infection, and isoimmunization.

As noted earlier, preterm and small-for-gestational age infants commonly are associated with breech labor and delivery. As for term breech infants, experience indicates that most of the adverse outcomes seen are unrelated to breech delivery. Thus, for all breech fetuses, about one third of the excessive perinatal loss falls to birth trauma and asphyxia.

COMPLICATIONS AND COUNSELING

The complications associated with abnormal fetal lie and malpresentations include both maternal and fetal. As noted earlier, prematurity and malpresentation are strongly related. Circumstances in which premature birth may occur also include maternal complications such as pregnancy-induced hypertension and medical complications (cardiovascular, neoplastic), as well as obstetric problems such as premature rupture of membranes and chorioamnionitis. The circumstances dictating delivery may further compromise the preterm fetus.

The obstetric complications for the fetus include a diverse group of misadventures. Prolapse of the umbilical cord, intrauterine infection, maldevelopment as a result of oligohydramnios, asphyxia, and birth trauma all are concerns.

Birth trauma, particularly to the head and cervical spine, is a significant risk to both term and preterm infants who present as breech presentation or in a nonaxial lie. 7 , 8 , 9 Unlike the cephalic fetus in whom hours of adaptation to the maternal bony pelvis (molding) may occur, the after-coming head of the breech fetus must descend and deliver rapidly and without significant change in shape. Therefore, small alterations in the dimensions or shape of the maternal bony pelvis or the attitude of the fetal head may have grave consequences. As discussed earlier, this process is of greater risk to the preterm infant because of the relative size of the fetal head and body. Trauma to the head is not eliminated by cesarean section; both intracranial and cervical spine trauma may result from entrapment in either the uterine or abdominal incisions. 10

The fetus in the transverse lie, regardless of gestational age, generally requires cesarean delivery. At cesarean section, delivery may be aided by converting the fetus to a longitudinal lie for the delivery after entering the abdomen. This conversion may allow for the use of a transverse incision into the uterus instead of the more morbid vertical incision.

External cephalic version (ECV) should be considered in a nonlaboring patient. When the diagnosis is first made at term, spontaneous conversion to a longitudinal lie is less common than for its breech counterpart. This results from the higher incidence of structural causes for the transverse lie.

When abnormal presentation or lie occurs in a twin gestation, management includes a greater range of options. The conversion of a backup transverse second twin, either by internal or external version at the time of delivery, is an option for the experienced clinician. When the back is down at the time of delivery, the prudent course for the delivery of a fetus in transverse lie is by cesarean section. Strong consideration should be given to the incisions at delivery in this circumstance, with a vertical uterine incision being used liberally.

When a fetus in a transverse lie is diagnosed remote from delivery, as occurs at time of ultrasound, the physician is faced with an additional dilemma. Spontaneous rupture of membranes may result in cord prolapse or compromise with the risk of fetal asphyxia. Delivery at the time of antepartum ultrasound before term may result in jeopardy because of prematurity. External version, as a correction, may be attempted as long as ultrasound excludes placenta previa and documents an appropriate amount of amniotic fluid. Experience has demonstrated some success, although in general, the use of ECV is more likely to be successful for a breech-presenting fetus.

The patient should be carefully counseled about the problem and its inherent risks. Hospitalization and observation may be considered. However, the cost–benefit ratio in this era of managed care makes prolonged hospitalization unlikely under most circumstances. I recommend twice-weekly fetal surveillance to assess for cord compromise. The patient should be warned about the signs and symptoms of preterm labor and encouraged to present to labor and delivery should these conditions arise. Under certain circumstances, home uterine activity monitoring may provide a useful adjunct.

The antepartum diagnosis of persistent breech presentation is accompanied by similar concerns. In addition, careful evaluation for fetal anomalies is warranted. A targeted ultrasound by an experienced ultrasonographer is useful to diagnosis structural fetal defects and to ascertain appropriate fetal growth. Prenatal diagnosis by maternal screening or amniocentesis may be indicated.

When premature rupture of membranes occurs, consideration of a timely delivery should ensue. Depending on gestational age, amniotic fluid volume, and cervical evaluation, a limited course of tocolysis, antibiotics, and steroid administration may be indicated. When a fetus with an abnormal lie or malpresentation presents under these circumstances, hospital care is best managed within the confines of labor and delivery, where fetal surveillance can be maintained on a continual basis. This is indicated primarily because of the risk of cord prolapse or compromise. With severe oligohydramnios, the high incidence of intrauterine infection adds measurably to the risks of maintaining the fetus in utero, and an expedited delivery is warranted routinely.

INTRAPARTUM COMPLICATIONS AND COUNSELING

As previously discussed, the new intrapartum diagnosis of a transverse lie generally results in an expedited cesarean delivery. When a transverse lie is associated with prolapse of the umbilical cord, a true obstetric emergency may arise. Pelvic examination, with relief of pressure against the umbilical cord, should be performed and parenteral tocolysis administered if contraindications are not present. Changes in maternal positioning, particularly the lateral supine position, usually are well tolerated by both patient and practitioner.

Transport to a delivery room equipped for cesarean delivery should be accomplished promptly. When setup is complete, abdominal delivery is performed. A consideration for a limited attempt at version may play a role in this clinical scenario after anesthesia has been satisfactorily obtained.

Clinically more common is the diagnosis of a breech presentation at or near term. Prenatal visits in the third trimester should include Leopold maneuvers and should frequently include ultrasound as an adjunct. Also, they should always include the consideration that malpresentation may exist. The diagnosis of this situation before the onset of labor should be the goal because this allows for a larger and safer range of options. 11

After a diagnosis is confirmed, the patient deserves as thorough an explanation as is called for by the specific situation. She likely has heard, at least peripherally, that a breech baby means a mandatory cesarean section.

Whereas there is some truth in this simple association, I strongly believe that as the patient's advocate, physicians undertake the responsibility to provide a fuller discussion. Most breech fetuses at term are not a complex problem. Most do not have congenital anomalies or other adverse obstetric problems. Their potential problem centers on the risks of asphyxia and trauma during labor and delivery.

Clearly, this group of risks, however clinicians clinically work to minimize them, are best avoided if possible. Therefore, the diagnosis of breech presentation before labor allows the patient to undergo ECV and hopefully delivery as a cephalic fetus (Fig. 4). ECV is a time-honored approach to correct a “malpresentation.” It was used in the past as soon as the diagnosis of a breech fetus was made. This led to many second-trimester and early third-trimester procedures. Given the size of the fetus and the quantity of amniotic fluid present, it is not surprising that the failure rate was high. Because most of these fetuses would have spontaneously converted to cephalic presentations at the time of labor, using ECV resulted in many unnecessary procedures 12 ( Table 7 ).

Table 7. Spontaneous conversion of breech to cephalic presentation

(Adapted from Westgren M, Edvall H, Nordstrom L et al: Spontaneous cephalic version of breech presentation in the last trimester. Br J Obstet Gynaecol 92:19, 1985)

In fact, the earlier practitioners of the 20th century used sufficient force to avoid the need for a cesarean section under these circumstances that general anesthesia was used, as well as regional anesthesia and analgesics. Unfortunately, the great forces were associated with serious trauma to the placenta and uterus. Spontaneous rupture of both the uterus and the membranes, placental abruption, and fetal isoimmunization also were seen and resulted in the abandonment of this approach.

ECV performed on a fetus at term and in the absence of maternal anesthesia or analgesia made a return to practice in the 1970s. 13 , 14 By performing ECV at term, spontaneous conversion reduced the population at need for a cesarean section for breech presentation. 12 By performing ECV at term and within the labor and delivery area, means were available for immediate cesarean delivery if a problem ensued. Several groups have demonstrated a high degree of success with ECV in the late third trimester. 15 , 16 , 17

Even under these circumstances and safeguards, ECV is not entirely risk free. Although usually of no clinical consequence, fetal bradycardia is common during the procedure. Antepartum bleeding, isoimmunization, and fetal death (acute and remote) have been described. 18 Furthermore, conversion may cause deflexion of the fetal head or result in a funic presentation, either of which might require a cesarean delivery in and of itself. 19 , 20

If ECV fails or if the patient finds it unacceptable, at least two further choices remain. The first is delivery by cesarean section. If the patient is a candidate, the second is a selective trial of labor.

Once the diagnosis of breech presentation has been confirmed and attempts at ECV have failed, both patient and physician require a heightened effort at communication to ensure that a plan of care is established that is mutually acceptable. Potential risks for the breech fetus approaching term include umbilical cord prolapse, prolapse of the fetus before complete cervical dilation is achieved, and a rapidly progressive labor, with delivery imminent on arrival or even en route to labor and delivery.

Prolapse of the umbilical cord is an unusual complication in a term fetus in the early stages of labor. Because a breech fetus presents a smaller and less complete covering to the pelvic inlet, this risk is greater for all breech fetuses in comparison with all cephalic fetuses. Among breech fetus, the less complete the flexion of the lower extremities—such as occurs in footling breech presentations—the greater the risk.

Other factors, however, play a role in mitigating or increasing this risk. The nonasphyxiated fetus generally possesses a turgid umbilical cord, coated in Wharton jelly. With normal blood flow, cord prolapse is unlikely, regardless of position. Prolapse of the cord also is decidedly more common in the second stage of labor, when maternal expulsive efforts result in expression of the uterine contents ( Table 8 ).

Table 8. External cephalic version late in pregnancy

The exception occurs when the cord is located as the most dependent fetal part at the onset of labor, as seen in funic presentations. Ultrasound examination, in conjunction with color Doppler scan, can help to locate the exact position of the umbilical cord and should be performed at the time of ECV.

Prolapse of the fetus before achieving full cervical dilation, particularly in a rapidly progressive labor, is another concern. The fetus most likely to experience adverse consequences from this complication has a low birth weight and usually is preterm. 21 The breech fetus that is incomplete in flexion (the single- and double-footling varieties) has a greater tendency to prolapse under this premature descent. Unfortunately, this group is disproportionately represented in fetuses delivering preterm. The most common breech fetuses, frank and complete presentations, comprise most breech fetuses at term. Their risk of cord prolapse, or body prolapse before second stage, is only marginally greater than their cephalic counterparts. Thus, the patient and physician confronted with a frank or complete breech presentation at term and after a failed attempt at ECV should be reassured that although these risks exist, their occurrence is rare, in the order of 1 to 3 per 1000. 22

What about the woman with extremely rapid labor, or the patient who resides at a great distance from the hospital? Delivery of a breech fetus requires an experienced clinician to ensure the maximum safety of both infant and mother. Serious consideration should be given to induction of labor at term, after fetal lung maturation is assured. Cervical ripening and induction of labor may be conducted in the same manner as for a cephalic fetus. By scheduling the delivery of a breech fetus, either by cesarean section or by induction, the proper resources, both personnel and equipment, can be assured. 23 , 24

If a cesarean section is chosen, appropriate arrangements can be made, as delineated earlier in reference to a scheduled induction of labor. Cesarean section before the onset of labor avoids the additional risks of both cord prolapse and body prolapse before complete dilation and is associated with a lessened risk of anesthesia for the parturient. 25

INTRAPARTUM MANAGEMENT

Cesarean delivery has been liberally used to decrease perinatal mortality and morbidity for the breech fetus. The potential to avoid birth trauma and asphyxia led to its application to a greater extent even in the early part of the 20th century, when the safety of cesarean delivery was in greater question. As its use increased, the perinatal mortality associated with a live, nonanomalous fetus at term dropped dramatically 26 (Fig. 5).

Wright, in 1959, 27 called for the exclusive use of cesarean delivery for breech fetuses. In this and earlier eras, prematurity, low birth weight, or congenital anomalies went untreated or undertreated, and so the only group of breech fetuses that had a chance for survival were those infants born of normal weight at term. With the avoidance of intrapartum asphyxia or birth trauma sustained during delivery, the outcome could be improved. Indeed, a great difference in outcome was attributed by some to the risks of labor and delivery 28 ( Table 9 ).

Table 9. Outcome of breech infants weighing more than 2500 g, 1973–1980

(Adapted from Weingold AB: The Management of Breech Presentation. In Iffy L, Charles C [eds]: Operative Perinatology, pp 357–553. New York, Macmillan, 1984)

Although the liberal use of cesarean delivery is indicated for breech fetuses, there is concern about whether its routine use is warranted. In a study by Green and coworkers, 29 the rate of cesarean delivery for breech increased from 22% to 94% on the same medical service over a 15-year interval. Despite this extensive application of cesarean delivery, the perinatal outcome, as measured by evidence of asphyxia, trauma, or intrapartum death, was unchanged ( Table 10 ).

Table 10. Outcome of breech presenting fetuses at term by method of delivery

Cesarean delivery increases maternal morbidity and mortality, albeit to a lesser extent than in the past. The relative risks and benefits to both mother and infant should be presented by the physician to the patient ( Table 11 ). The cost, both economic and psychological, of cesarean delivery also has been debated. In past eras, a greater dollar cost was associated with abdominal delivery. With shorter stays and improved approaches to cesarean delivery, the difference has narrowed.

Table 11. Perinatal and maternal morbidity associated with breech labor and delivery

Another approach is the selective use of a trial of labor. By identifying which breech fetuses and mothers have the greatest predictable risk, cesarean delivery can be used for the group likely to have the greatest gain. By avoiding cesarean delivery in the low-risk pairings, use of cesarean delivery can be minimized, with subsequent savings to the health system of limited resources.

Many authors realize the potential benefits of such an approach. 30 , 31 , 32 At a 4% incidence and at 4 million births a year, some 160,000 pregnancies are complicated by a breech-presenting fetus at term on an annual basis. At a rate of cesarean delivery of about 90%, this results in 144,000 procedures, almost one-fifth that of cesarean delivery. By selecting a low-risk group for a trial of labor, the overall use of cesarean delivery for this indication might be reduced to 50%, saving more than 60,000 major surgeries a year, or 8% of the total cesarean deliveries performed.

This savings would be moot if there were a corresponding increase in perinatal morbidity and mortality associated with this practice shift. The available data on selective trials of labor support such an approach and suggest that the additional fetal risk is minimal and justified by the reduction in maternal morbidity and mortality.

Some of the factors for consideration in determining the risks for an individual patient already have been mentioned. Given the size and shape of the low birth weight breech fetus, most authors agree that fetuses who are breech and require delivery between 1000 and 2000 g are best served by cesarean delivery. The group of preterm fetuses weighing less than 1000 g and in need of delivery require individual assessment. The trauma to be avoided at vaginal delivery may occur at cesarean delivery. The need for vertical uterine incisions, which may require extension into the fundus, makes breech extraction difficult. This is particularly true in the presence of ruptured membranes. Entrapment of the after-coming head is of particular concern in this weight group. As outlined earlier, the head–abdomen ratio and the incidence if “incomplete” types of breech fetuses are predisposing factors. Entrapment occurs at both cesarean delivery and vaginal deliveries with these low birth weight infants. Delivery “en caul” may mitigate against head entrapment at cesarean delivery or vaginal delivery after the delivery of the small fetus.

At the other extreme, the macrosomic breech fetus also is an indication for cesarean delivery. Even with a favorable head–abdomen ratio at term, dystocia may be encountered with the delivery of either the fetal abdomen or after-coming head.

When the fetal head is extended, there is increased concern for the safety of delivery by either route. 8 , 33 A careful evaluation by radiograph or ultrasound should be a part of the predelivery examination of a patient with a breech fetus, regardless of the route of delivery chosen. 34 Extension of the after-coming head, diagnosed as an angle of greater than 105 degrees between the mandible and the cervical spine, may compromise the cervical spinal cord during delivery (see Fig. 1). Extension is uncommon (less than 5%) and may result from fetal goiter, a nuchal cord, or abnormalities of the shape of the uterine cavity. Additionally, extension may be caused by, or may be a sign of, fetal neurologic compromise, with an inability of the fetus to adequately flex his head on his chest. Extension should result in delivery by cesarean delivery. Extra care should be taken at cesarean delivery to cause the fetal head to flex during delivery by applying force on the fetal head during delivery. This ameliorates the tendency to fetal extension that occurs with the breech extraction used by some in a cesarean delivery. 35

Prolapse of the umbilical cord is decidedly rare in the first stage of labor. However, with single- and double-footling breech fetuses, the risk increases greatly during the second stage. Therefore, some authors exclude these specific types of breech fetuses from consideration for a trial of labor.

For the more common frank and complete types of breech presentation, the risk of cord prolapse is the same or only marginally greater than for a cephalic fetus. It is within this group, who constitute most breech fetuses at term, that a selective trial of labor will have the greatest benefit 36 ( Table 12 ).

Table 12. Selection characteristics for a trial of labor in a breech presentation

Measurement of the bony pelvis is performed to exclude borderline pelvic diameters. I advocate the use of radiologic measurement of the maternal bony pelvis. Computed tomography scan reliably measures pelvic dimensions and the attitude of the fetal head. Magnetic resonance imaging also has been successfully used in this setting. 37 The outcome of term breech delivery may be facilitated by only allowing a trial in women with pelvic measurements shown to be associated with successful breech delivery. 38 Todd and Steer, 6 in reviewing more than 1000 breech deliveries at term, demonstrated a critical difference in perinatal outcome when the pelvic inlet measured greater than 12 cm at the transverse of the inlet, and greater than 11 cm for the AP diameter. Gimovsky and associates 38 expanded this to include a midpelvic diameter of greater than 10 cm ( Table 13 ). Several authors have demonstrated the efficacy of this measure. 39 The use of computed tomography scanning results in a limited exposure of the fetus to ionizing radiation. 40 An additional benefit is the reproducibility and ease with which pelvic measurements may be obtained.

Table 13. Results of X-ray pelvimetry in a group of women undergoing a successful trial of labor under protocol

Typically, three views are obtained (Fig. 6). Because most patients will have undergone a failed attempt at ECV, I obtain pelvimetry at that time for the patient selected for a trial of labor. Patients in whom we are unable to convert a breech presentation are unlikely to undergo spontaneous conversion. Alternatively, pelvimetry may be obtained on presentation in early labor.

MANAGEMENT OF LABOR AND DELIVERY

When a trial of labor is undertaken with a breech-presenting fetus, it is crucial for an expedited cesarean delivery to be continuously available. The usual indicators of fetal well-being, as well as the adequacy of the progression of labor, will give rise to the indication for cesarean delivery on occasion. The criteria clinically used in supervising the labor of a cephalic fetus should be applied to the selected term breech fetus. In my experience, as well as others, cervical ripening, oxytocin induction, and partographic analysis of labor are safe and efficacious. Augmentation, when indicated, should call for a thoughtful re-evaluation of all aspects of the situation. For example, is the fetal size less than 4000 g? Has descent occurred progressively during the second stage? Have adequate maternal expulsive efforts failed to effect “crowning?” Oxytocin augmentation should be used only after an internal pressure transducer indicates inadequate contractions. Cesarean delivery should be used liberally in all other circumstances.

Fetal surveillance during labor and delivery should be continuous. After spontaneous rupture of membranes, internal monitoring may be used. Fetal heart rate patterns, particularly in the second stage of labor, may have pronounced variable decelerations. In breech labor and delivery, compromise to the umbilical circulation may be more frequent but generally is without sequelae. In addition, the intensity and duration of vagal stimulation with its concomitant effects on the fetal heart rate is different than in cephalic labor and delivery. Study of acid–base status at birth demonstrates a tendency to respiratory acidosis in breech vaginal delivery. This might explain a greater proportion of infants with lower Apgar scores at 1 minute. However, the base deficit in these infants generally is within the normal range. 41

Anesthesia considerations dictate the usefulness of regional anesthesia, as opposed to earlier approaches that used a combination of local and general techniques. As shown by Crawford, 42 regional anesthesia prevents premature maternal expulsive efforts, which should enhance the safety of delivery ( Table 14 ).

Table 14. Effect of anesthesia on breech delivery

(Adapted from Weingold AB: The Management of Breech Presentation. In Iffy L, Charles D [eds]: Operative Perinatology, pp 537–553. New York, Macmillan, 1984)

The second stage of labor should be managed under double-setup conditions. A gowned and gloved assistant, as well as anesthesia and pediatrics personnel, should be present. The patient should be instructed and encouraged to push effectively. The fetal heart rate should be continuously monitored. A nullipara should be allowed to push for up to 2 hours, a multipara up to 1 hour. If delivery is not imminent, cesarean delivery should be performed, the diagnosis being a failure of descent.

After lateral flexion of the trunk, the anterior hip is forced against and underneath the symphysis. Expulsion follows, with delivery of the anterior and then the posterior buttock. During “crowning,” an episiotomy should be performed to facilitate delivery.

Using a modified Bracht maneuver, a warm wet towel is placed around the fetal abdomen, and the fetus is grasped on the posterior aspect of the fetal pelvic girdle with care to avoid the fetal kidneys and adrenal. A gentle downward traction is exerted.

After the buttocks are fully expulsed, the back is born by rotation anteriorly. This allows the shoulders to enter the pelvis in the transverse diameter of the pelvic inlet. If there is a failure of anterior rotation, the fetus will be born as a posterior breech, and the sequence of maneuvers used to help in delivery will differ as appropriate.

As the anterior shoulder is seen at the introitus, the operator sweeps the right humerus across the infant's chest. Gentle rotation allows for the posterior shoulder and humerus to be born, completing the Løvset maneuver (Fig. 7).

With the infant delivered to the umbilicus, some authors recommend the use of uterine relaxants to facilitate the remainder of the delivery. The use of general anesthesia with halothane has been supplanted by parenteral betamimetics. We have used small aliquots of intravenous nitroglycerin for this purpose. 43 , 44

Delivery of the after-coming head follows with manual aid or forceps.

A Mauriceau–Smellie–Viet maneuver follows (Fig. 8). The fetus is placed abdomen down on the operator's right arm. The left hand supports the fetal neck. The index and middle fingers of the right hand are placed on the fetal maxilla to help maintain flexion of the head. The assistant may apply suprapubic pressure to expel the after-coming head (Naujok maneuver; Fig. 9). When delivery is further complicated by rotation of the fetal back posteriorly, a Prague maneuver allows for delivery of the occiput posterior breech variant.

Forceps may be used to facilitate delivery of the after-coming head (Fig. 10). Maintenance of head flexion is crucial. Traction is not required. The Piper forceps are specially designed for this task 45 and act as a class 1 lever. Because the fetal head is visible and should be aligned as in an occiput anterior position, any outlet forceps that may be applied as a simple pelvic application are indicated. Elliott forceps are particularly useful in this situation. Use of forceps may be helpful in a nulligravida or when the fetus is small and at term (less than 2500 g).

The infant then should be handed to the pediatrician in attendance. A segment of umbilical cord for acid–base analysis should be routinely obtained. Attention then can be directed to completion of the third stage of labor, as well as the repair of the episiotomy and genital tract lacerations.

A full dictated operative note should be completed at the time of delivery. The entire process of the labor, delivery, and immediate neonatal outcome should be referenced. Mention of each specific step is warranted, along with clinical observations regarding the relative ease or difficulty of the delivery process.

CESAREAN DELIVERY

Most breech-presenting fetuses will be born by cesarean delivery. Attention to the details of delivery are of no less consequence in this group.

When cesarean delivery is selected, the fetus should be evaluated before surgery using bedside ultrasound examination. A careful review of the fetus to diagnose extension of the head, the presence or absence of nuchal arms, and the location of the placenta should be made. Although estimates of fetal weight may be less accurate for breech-presenting fetuses, an estimated fetal weight should be made using a standardized formula. 46 Amniotic fluid volume and location of the umbilical cord also should be observed.

These observations may be important in understanding neonatal concerns after cesarean delivery. They allow both physician and patient to estimate the fetal condition just before birth. Important observations that have been confirmed before delivery include the presence of abnormal postures, broken bones, and the occasional transverse lie (or even an undiagnosed second twin).

Cesarean delivery should be expedited if the patient is in labor. Short-term tocolysis has been used so that the most appropriate anesthesia can be administered. Emergency cesarean delivery, with the greater risks of morbidity for both mother and child, should be chosen as a last resort.

The abdomen generally is opened with a transverse-type incision. Surgical choice of incision may vary by maternal habitus, prior surgery, or operator preference. Any incision may be used, as long as adequate visualization occurs and mobilization of the fetus is expedited.

Palpation of the uterus before the uterine incision should confirm the presentation. A low cervical transverse incision should be made carefully in the midline and extended to a depth necessary to expose the membranes. This is easier to do in practice if the membranes are intact. The important point is that the fetus may be incidentally incised if care is not taken. The infant born by cesarean delivery should be carefully examined after birth in this regard.

The fetus should be rotated (if necessary) so that the back is anterior before delivery. The assistant applies fundal pressure as the operator guides the buttocks up through the uterine incision. The use of force on the fundus allows the after-coming head of the breech fetus to remain in a flexed attitude. This approach also should minimize the loss of flexion of the fetal arms, which may result in a nuchal displacement.

A warm, wet towel is wrapped around the fetal abdomen to protect the fetus from traumatic injury and to mitigate against the onset of breathing movements before delivery.

Thus, by the use of an assistant giving fundal pressure, delivery of a breech fetus at cesarean delivery mirrors an assisted vaginal breech delivery. Avoid total breech extraction at cesarean delivery: it is inherently more of a risk to the fetus than an assisted or spontaneous breech delivery.

As with vaginal delivery, a section of umbilical cord should be sent for acid–base status. Attention is given to the description of the delivery process within the operative report.

PERINATAL OUTCOME

The most important factor in neonatal outcome for all infants is gestational age. This also is true for breech infants.

Many series, generally retrospective, some aided by meta-analysis, have studied the effect of mode of delivery on both immediate and long-term outcome. In the absence of congenital anomalies, laboring fetuses born ultimately by cesarean or vaginal delivery have similar outcomes, which are determined by gestational age and weight. Prolapse of the umbilical cord that occurs before hospitalization or goes unrecognized, although uncommon at term, plays a serious and compromising role for preterm infants. Such also is the case for prolapse of the fetal body through an incompletely dilated cervix. Entrapment of the after-coming head may have serious adverse consequences for the infant who likewise is preterm. This may occur at either cesarean or vaginal delivery.

Infants who are born immediately after admission to labor and delivery also have the greatest risk of asphyxia- and trauma-related injuries manifest in the immediate neonatal period. Women and their fetuses in whom breech presentation is not detected until labor, and who ultimately are delivered by cesarean delivery are subject to the greatest risk of maternal morbidity. 47

Regardless of the rate of cesarean delivery, breech infants have an increased risk of perinatal and neonatal morbidity and mortality. Cesarean delivery plays a role in decreasing but not eliminating this problem. Breech-presenting infants have higher rates of neurologic sequelae than their cephalic peers. The route of delivery plays little role in this difference. 48 .

The International Term Breech Trial 47 , 48 , 49 was undertaken to determine the best approach to term breech delivery management. This trial proved to be limited and controversial in several repects 49 and, subsequently, the PREMODA trial 50 was reported. With a much larger cohort studied, the authors determined that there was no difference in the neonatal outcome between vaginal and cesarean delivery in the term frank breech fetus. Consequently, the American College of Obstetricians and Gynecologists issued a revised Committee Opinion (#340, July 2006) concluding that with adaptation of strict protocol management and based on provider experience, a trial of labor for the term frank breech fetus was an acceptable option. 51 A Practice Bulletin from the Society of Obstetricians and Gynecologists of Canada in 2009 was in agreement with this selective approach to delivery management. 52  

The issues encountered in attempting to reach the optimal outcome for every pregnancy complicated by breech presentation include psychological, sociologic, and societal values. A strictly medical paradigm cannot perfectly fit each individual situation. Thus, a variety of approaches conform to the standard of care for medical practice. Resident training in breech delivery should include both the approach to delivery at cesarean section as well as vaginal delivery. 53 All parties involved must understand the risks and benefits of any suggested approaches. Because economic concerns have been emphasized more, a shift of decision making from the individual patient–physician pair to the consideration of the entire population has occurred. Both strategies must be made consistent.

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Abnormal Fetal Presentation

Abnormal Fetal Presentation Roya Sohaey, MD DIFFERENTIAL DIAGNOSIS Common Occiput-Posterior Complete Breech Frank Breech Footling Breech Less Common Transverse Lie Incomplete Breech Rare but Important Funic Presentation ESSENTIAL INFORMATION Key Differential Diagnosis Issues Normal presentation at term Vertex and occiput-anterior Back of head faces pubis 43% vertex at 15-22 weeks 90% vertex at 31-35 weeks 3-4% of term fetuses are breech 87% deliver by cesarean section External cephalic version 40% success in nulliparous women 60% success in multiparous women Etiology of malpresentation Idiopathic Prematurity Placenta previa Uterine anomaly Abnormal fetal movement Helpful Clues for Common Diagnoses Occiput-Posterior Vertex + face to pubis Vaginal delivery attempted Labor typically longer Complete Breech Buttocks presenting Flexed legs (feet down) Frank Breech Buttocks presenting Extended legs (feet up) Footling Breech Foot or feet presenting Helpful Clues for Less Common Diagnoses Transverse Lie Fetus is sideways Head in one flank, bottom in other Obligatory cesarean delivery Incomplete Breech Hybrid of complete and frank breech One leg extended and one leg flexed Helpful Clues for Rare Diagnoses Funic Presentation Umbilical cord slips in front of fetus More common with nonvertex presentation Cord may prolapse into vagina Emergency cesarean delivery Other Essential Information Twins Presenting twin vertex for vaginal delivery Second twin position less important Image Gallery Sagittal ultrasound shows a late term fetus in a cephalic position; however, the face , not the occiput, is facing the anterior uterine wall. The finding may be relevant if the patient is in active labor.

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StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

StatPearls [Internet].

Delivery, face and brow presentation.

Julija Makajeva ; Mohsina Ashraf .

Affiliations

Last Update: January 9, 2023 .

• Continuing Education Activity

Face and brow presentation is a malpresentation during labor when the presenting part is either the face or, in the case of brow presentation, it is the area between the orbital ridge and the anterior fontanelle. This activity reviews the evaluation and management of these two presentations and explains the role of the interprofessional team in managing delivery safely for both the mother and the baby.

• Describe the mechanism of labor in the face and brow presentation.
• Summarize potential maternal and fetal complications during the face and brow presentations.
• Review different management approaches for the face and brow presentation.
• Outline some interprofessional strategies that will improve patient outcomes in delivery cases with face and brow presentation issues.
• Introduction

The term presentation describes the leading part of the fetus or the anatomical structure closest to the maternal pelvic inlet during labor. The presentation can roughly be divided into the following classifications: cephalic, breech, shoulder, and compound. Cephalic presentation is the most common and can be further subclassified as vertex, sinciput, brow, face, and chin. The most common presentation in term labor is the vertex, where the fetal neck is flexed to the chin, minimizing the head circumference.

Face presentation – an abnormal form of cephalic presentation where the presenting part is mentum. This typically occurs because of hyperextension of the neck and the occiput touching the fetal back. Incidence of face presentation is rare, accounting for approximately 1 in 600 of all presentations. [1] [2] [3]

In brow presentation, the neck is not extended as much as in face presentation, and the leading part is the area between the anterior fontanelle and the orbital ridges. Brow presentation is considered the rarest of all malpresentation with a prevalence of 1 in 500 to 1 in 4000 deliveries. [3]

Both face and brow presentations occur due to extension of the fetal neck instead of flexion; therefore, conditions that would lead to hyperextension or prevent flexion of the fetal neck can all contribute to face or brow presentation. These risk factors may be related to either the mother or the fetus. Maternal risk factors are preterm delivery, contracted maternal pelvis, platypelloid pelvis, multiparity, previous cesarean section, black race. Fetal risk factors include anencephaly, multiple loops of cord around the neck, masses of the neck, macrosomia, polyhydramnios. [2] [4] [5]

These malpresentations are usually diagnosed during the second stage of labor when performing a digital examination. It is possible to palpate orbital ridges, nose, malar eminences, mentum, mouth, gums, and chin in face presentation. Based on the position of the chin, face presentation can be further divided into mentum anterior, posterior, or transverse. In brow presentation, anterior fontanelle and face can be palpated except for the mouth and the chin. Brow presentation can then be further described based on the position of the anterior fontanelle as frontal anterior, posterior, or transverse.

Diagnosing the exact presentation can be challenging, and face presentation may be misdiagnosed as frank breech. To avoid any confusion, a bedside ultrasound scan can be performed. [6]  The ultrasound imaging can show a reduced angle between the occiput and the spine or, the chin is separated from the chest. However, ultrasound does not provide much predicting value in the outcome of the labor. [7]

• Anatomy and Physiology

Before discussing the mechanism of labor in the face or brow presentation, it is crucial to highlight some anatomical landmarks and their measurements. 

Planes and Diameters of the Pelvis

The three most important planes in the female pelvis are the pelvic inlet, mid pelvis, and pelvic outlet. 

Four diameters can describe the pelvic inlet: anteroposterior, transverse, and two obliques. Furthermore, based on the different landmarks on the pelvic inlet, there are three different anteroposterior diameters, named conjugates: true conjugate, obstetrical conjugate, and diagonal conjugate. Only the latter can be measured directly during the obstetric examination. The shortest of these three diameters is obstetrical conjugate, which measures approximately 10.5 cm and is a distance between the sacral promontory and 1 cm below the upper border of the symphysis pubis. This measurement is clinically significant as the fetal head must pass through this diameter during the engagement phase. The transverse diameter measures about 13.5cm and is the widest distance between the innominate line on both sides. 

The shortest distance in the mid pelvis is the interspinous diameter and usually is only about 10 cm. 

Fetal Skull Diameters

There are six distinguished longitudinal fetal skull diameters:

• Suboccipito-bregmatic: from the center of anterior fontanelle (bregma) to the occipital protuberance, measuring 9.5 cm. This is the presenting diameter in vertex presentation. 
• Suboccipito-frontal: from the anterior part of bregma to the occipital protuberance, measuring 10 cm 
• Occipito-frontal: from the root of the nose to the most prominent part of the occiput, measuring 11.5cm
• Submento-bregmatic: from the center of the bregma to the angle of the mandible, measuring 9.5 cm. This is the presenting diameter in face presentation where the neck is hyperextended. 
• Submento-vertical: from the midpoint between fontanelles and the angle of the mandible, measuring 11.5cm 
• Occipito-mental: from the midpoint between fontanelles and the tip of the chin, measuring 13.5 cm. It is the presenting diameter in brow presentation. 

Cardinal Movements of Normal Labor

• Neck flexion
• Internal rotation
• Extension (delivers head)
• External rotation (Restitution)
• Expulsion (delivery of anterior and posterior shoulders)

Some of the key movements are not possible in the face or brow presentations.  

Based on the information provided above, it is obvious that labor will be arrested in brow presentation unless it spontaneously changes to face or vertex, as the occipito-mental diameter of the fetal head is significantly wider than the smallest diameter of the female pelvis. Face presentation can, however, be delivered vaginally, and further mechanisms of face delivery will be explained in later sections.

• Indications

As mentioned previously, spontaneous vaginal delivery can be successful in face presentation. However, the main indication for vaginal delivery in such circumstances would be a maternal choice. It is crucial to have a thorough conversation with a mother, explaining the risks and benefits of vaginal delivery with face presentation and a cesarean section. Informed consent and creating a rapport with the mother is an essential aspect of safe and successful labor.

• Contraindications

Vaginal delivery of face presentation is contraindicated if the mentum is lying posteriorly or is in a transverse position. In such a scenario, the fetal brow is pressing against the maternal symphysis pubis, and the short fetal neck, which is already maximally extended, cannot span the surface of the maternal sacrum. In this position, the diameter of the head is larger than the maternal pelvis, and it cannot descend through the birth canal. Therefore the cesarean section is recommended as the safest mode of delivery for mentum posterior face presentations. 

Attempts to manually convert face presentation to vertex, manual or forceps rotation of the persistent posterior chin to anterior are contraindicated as they can be dangerous.

Persistent brow presentation itself is a contraindication for vaginal delivery unless the fetus is significantly small or the maternal pelvis is large.

Continuous electronic fetal heart rate monitoring is recommended for face and brow presentations, as heart rate abnormalities are common in these scenarios. One study found that only 14% of the cases with face presentation had no abnormal traces on the cardiotocograph. [8] It is advised to use external transducer devices to prevent damage to the eyes. When internal monitoring is inevitable, it is suggested to place monitoring devices on bony parts carefully. 

People who are usually involved in the delivery of face/ brow presentation are:

• Experienced midwife, preferably looking after laboring woman 1:1
• Senior obstetrician 
• Neonatal team - in case of need for resuscitation 
• Anesthetic team - to provide necessary pain control (e.g., epidural)
• Theatre team  - in case of failure to progress and an emergency cesarean section will be required.
• Preparation

No specific preparation is required for face or brow presentation. However, it is essential to discuss the labor options with the mother and birthing partner and inform members of the neonatal, anesthetic, and theatre co-ordinating teams.

• Technique or Treatment

Mechanism of Labor in Face Presentation

During contractions, the pressure exerted by the fundus of the uterus on the fetus and pressure of amniotic fluid initiate descent. During this descent, the fetal neck extends instead of flexing. The internal rotation determines the outcome of delivery, if the fetal chin rotates posteriorly, vaginal delivery would not be possible, and cesarean section is permitted. The approach towards mentum-posterior delivery should be individualized, as the cases are rare. Expectant management is acceptable in multiparous women with small fetuses, as a spontaneous mentum-anterior rotation can occur. However, there should be a low threshold for cesarean section in primigravida women or women with large fetuses.

When the fetal chin is rotated towards maternal symphysis pubis as described as mentum-anterior; in these cases further descend through the vaginal canal continues with approximately 73% cases deliver spontaneously. [9] Fetal mentum presses on the maternal symphysis pubis, and the head is delivered by flexion. The occiput is pointing towards the maternal back, and external rotation happens. Shoulders are delivered in the same manner as in vertex delivery.

Mechanism of Labor in Brow Presentation

As this presentation is considered unstable, it is usually converted into a face or an occiput presentation. Due to the cephalic diameter being wider than the maternal pelvis, the fetal head cannot engage; thus, brow delivery cannot take place. Unless the fetus is small or the pelvis is very wide, the prognosis for vaginal delivery is poor. With persistent brow presentation, a cesarean section is required for safe delivery.

• Complications

As the cesarean section is becoming a more accessible mode of delivery in malpresentations, the incidence of maternal and fetal morbidity and mortality during face presentation has dropped significantly. [10]

However, there are still some complications associated with the nature of labor in face presentation. Due to the fetal head position, it is more challenging for the head to engage in the birth canal and descend, resulting in prolonged labor.

Prolonged labor itself can provoke foetal distress and arrhythmias. If the labor arrests or signs of fetal distress appear on CTG, the recommended next step in management is an emergency cesarean section, which in itself carries a myriad of operative and post-operative complications.

Finally, due to the nature of the fetal position and prolonged duration of labor in face presentation, neonates develop significant edema of the skull and face. Swelling of the fetal airway may also be present, resulting in respiratory distress after birth and possible intubation.

• Clinical Significance

During vertex presentation, the fetal head flexes, bringing the chin to the chest, forming the smallest possible fetal head diameter, measuring approximately 9.5cm. With face and brow presentation, the neck hyperextends, resulting in greater cephalic diameters. As a result, the fetal head will engage later, and labor will progress more slowly. Failure to progress in labor is also more common in both presentations compared to vertex presentation.

Furthermore, when the fetal chin is in a posterior position, this prevents further flexion of the fetal neck, as browns are pressing on the symphysis pubis. As a result, descend through the birth canal is impossible. Such presentation is considered undeliverable vaginally and requires an emergency cesarean section.

Manual attempts to change face presentation to vertex, manual or forceps rotation to mentum anterior are considered dangerous and are discouraged.

• Enhancing Healthcare Team Outcomes

A multidisciplinary team of healthcare experts supports the woman and her child during labor and the perinatal period. For a face or brow presentation to be appropriately diagnosed, an experienced midwife and obstetrician must be involved in the vaginal examination and labor monitoring. As fetal anomalies, such as anencephaly or goiter, can contribute to face presentation, sonographers experienced in antenatal scanning should also be involved in the care. It is advised to inform the anesthetic and neonatal teams in advance of the possible need for emergency cesarean section and resuscitation of the neonate. [11] [12]

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Disclosure: Julija Makajeva declares no relevant financial relationships with ineligible companies.

Disclosure: Mohsina Ashraf declares no relevant financial relationships with ineligible companies.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

• Cite this Page Makajeva J, Ashraf M. Delivery, Face and Brow Presentation. [Updated 2023 Jan 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

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• Sonographic diagnosis of fetal head deflexion and the risk of cesarean delivery. [Am J Obstet Gynecol MFM. 2020] Sonographic diagnosis of fetal head deflexion and the risk of cesarean delivery. Bellussi F, Livi A, Cataneo I, Salsi G, Lenzi J, Pilu G. Am J Obstet Gynecol MFM. 2020 Nov; 2(4):100217. Epub 2020 Aug 18.
• Review Sonographic evaluation of the fetal head position and attitude during labor. [Am J Obstet Gynecol. 2022] Review Sonographic evaluation of the fetal head position and attitude during labor. Ghi T, Dall'Asta A. Am J Obstet Gynecol. 2022 Jul 6; . Epub 2022 Jul 6.
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